The present invention relates generally to the extrusion of synthetic polymeric material into filaments for use in textile manufacture and, more particularly, to the collection of a tow of multiple extruded filaments into a container in preparation for subsequent filament processing.
In the conventional manufacture of synthetic textile yarns, a molten polymeric material is extruded in the form of multiple continuous filaments which, after quenching to cool the filaments below their glass transition temperature, are gathered and transported longitudinally in a lengthwise coextensive bundle commonly referred to as a tow. A driven take-up unit disposed downstream of the extruding apparatus delivers the tow at a controlled transport speed to a so-called canning station at which the tow is deposited into an open-top can or like container for storage pending further processing. In a typical subsequent drawing operation, the tows from a plurality of thusly filled cans are placed in a common creel for delivery and processing in side-by-side parallel warp sheet form through a draw frame to subject the tows simultaneously to a stretching and heat setting operation to orient the molecular structure of each constituent filament in each tow.
Conventionally, the process of extruding filaments and forming tow therefrom and the downstream canning of the tow require a relatively significant overall vertical elevation to allow for downward extrusion of the filaments and subsequent downward depositing of the tow into cans. Accordingly, for considerations of efficient use of manufacturing space, the extrusion of filaments and formation thereof into tow is commonly carried out on an upper floor of the manufacturing plant, with the take-up unit being positioned on such floor to deliver the tow downwardly to the canning station on the floor immediately therebelow. A pair of driven so-called sunflower wheels are commonly utilized immediately following the take-up unit to provide controlled delivery of the tow downwardly to the canning station, the sunflower wheels conventionally being the last components to physically contact the tow prior to being deposited into a can. The sunflower wheels basically comprise cylindrical rolls having a plurality of rounded tooth-like protrusions equally spaced about their respected peripheries, with the wheels arranged in parallel spaced relation and independently driven for sufficiently close meshing of the protrusions without direct contact thereof to effect a gripping mode of transport of the tow downwardly to the canning station at the floor below without damaging the tow.
Precise control of the canning operation is critical to ensure the tow is deposited uniformly from one can to another and also uniformly within each given can, so that each filled can contains precisely the same mass of tow and to promote reliable and consistent withdrawal of the tow from each can. For this purpose, the tow cans are fabricated preferably of a rectangular cross-section and are supported at the canning station on a platform controlled to move back and forth in a first "x" direction a distance equivalent to the width of the can and to move indexably in a perpendicular "y" direction by a distance equivalent to the cross-sectional diameter of the tow at the completion of each movement in the "x" direction. In this manner, the canning station serves to lay the tow within the can in a serpentine fashion precisely across the full width and length of the can and to progressively build rows and layers of the tow in such manner until a predetermined mass of tow has been deposited.
Within limits, this tow canning process has proven to be reasonably effective and reliable for the described purpose. However, as the textile industry continually strives to improve efficiency and reduce manufacturing costs, much effort has been devoted to attempts to increase the number of filaments bundled in each tow and to increase the lineal speed at which the filaments are extruded and transported to the canning station. The attendant corresponding increase in the mass and momentum of the traveling tow as it is deposited into a can at the canning station tends to cause the incoming tow to impinge with sufficient force on previous layers to make it difficult and sometimes impossible to maintain the tow in precise serpentine rows and layers as intended. As a result, it has been found in practice that the tow in adjacent rows and layers can become entangled and, in turn, problems are experienced in withdrawing the tow from the can in subsequent process operations, e.g., at the draw frame. At such higher linear traveling speeds, the tow can also experience undesired deviations from its intended compact cross-sectional shape as a result of a tendency of the individual constituent filaments to flair or otherwise separate from one another over the final segment of its path of travel into the can during which the tow travels essentially unconfined through an open air space. Likewise, since the textile industry has similarly sought to progressively increase the operating speed of draw frames, the tows must be withdrawn from the cans in the draw frame creel at correspondingly increasing speeds, which can additionally aggravate entanglements in the tows.
Such tangles may often be manifested as a knot in the traveling tow, which will normally actuate stop motion detectors in the draw frame, causing the drawing operation to stop until an operator can manually intervene to disentangle the knotted tow. As will be appreciated, not only does such a stoppage of the drawing operation reduce the overall efficiency of the manufacturing operation, stoppages of the draw frame inherently pose the risk of localized overheating and attendant damage to the tows across the entire warp sheet. Furthermore, smaller knots or tangles in the tow which go undetected within the draw frame can cause even more severe problems in subsequent operations. For example, it is common to transport the warp sheet of drawn and heat-set tows exiting the draw frame through a pair of highly pressurized nip rolls and therefrom into a crimping apparatus commonly referred to as a stuffer box. The pressure exerted by the nip rolls can reach a magnitude on the order of twenty tons of force applied to the warp sheet and, hence, even very small knots or tangles in the tows will be unable to pass between the nip rolls and accordingly can result in severe damage to the support bearings for the rolls.
To date, little development work is known to have been devoted to addressing these problems. Fleissner GmbH & Co. of Egelsbach, Germany, has proposed a modified form of sunflower wheel arrangement wherein the two wheels are equipped with multiple projecting plates replacing in number the normally rounded and more shallow conventional teeth-like projections to attempt to achieve the dual function of gripping and transporting the tow and simultaneously slowing its traveling speed by imposing a zig-zag folding motion laterally with respect to the tow. It is believed, however, that in practice this modified sunflower wheel arrangement has limited effectiveness in its potential for reducing the traveling speed of the tow due to the high number of contact points between the projecting plates of the modified sunflower wheel and the tow. Although the high number of contact points of the modified sunflower wheel design is required for gripping and ensuring the desired traveling speed of the tow, it has been known to exhibit a greater tendency to stretch the relatively delicate tow and create a greater risk of breaking individual filaments. While reasonably effective to prevent tangling of the tow when deposited into a can, the resultant damage to the tow renders the tow largely unusable.